Her cousin wanted her to buy three boxes of Abbott baby formula, sold under the brand name Similac, and ship it to him in China. She did some research and found out the shipping alone could cost $80. "They're not from a very well-off family, and that really surprised me," she said — especially because they can buy Abbott baby formula in stores in China.

People in China's growing middle class are buying more and more foreign goods, which are widely available in stores in China. But baby formula is a special case.

"If China cannot even handle baby food, what can we trust?" Shane Li told me. Li, who lives in southern China, takes a 90-minute boat ride to Hong Kong every few weeks to buy formula, mashed baby food and bottles. Most of the products Li buys in Hong Kong are sold in stores near his house — same brands, same ingredients.

Abbott and other Western baby formula companies say they hold their factories in China to the same standards as everywhere else. Many people in China take them at their word — lots of people still buy formula in China. But there are enough people, like Shane Li, who distrust anything even packaged inside China to cause a disturbance in other parts of the world.

In the U.K., stores are rationing formula this month because of a shortage reportedly driven by people buying up formula and sending it to China. The Hong Kong government instituted limits and is now arresting people caught exiting with more than two containers of formula. In New York's Chinese neighborhoods, small shipping companies told me they have customers who send U.S. baby formula home to China every week.

When people in China buy formula from Hong Kong or the U.S., they're paying for regulations and standards they trust. And the growing class of Chinese people with a little extra money in their pockets will keep buying baby formula from overseas until the Chinese government convinces them to trust it, too.